Ajustes anatômicos e fisiológicos revelam mecanismos de sobrevivência em mudas sob déficit hídrico

Abstract

Some tropical forests experience prolonged droughts, making it essential to understand species' drought resistance mechanisms. Anatomical traits related to hydraulic architecture explain how water transport occurs in plants and how species cope with water scarcity. However, the ability of species to adjust their hydraulic architecture to water availability remains unclear. We assessed variations in hydraulic architecture and physiological responses to drought, focusing on the coordination between anatomical and physiological traits. This study was conducted in a greenhouse with seedlings of three tropical species: Clitoria fairchildiana, Manilkara elata, and Bertholletia excelsa. We applied three water availability treatments (15%, 50%, and 100% of field capacity) for four months. We measured branch anatomical traits: Vessel area (VA), Hydraulic diameter (Dh), Vessel density (VD), Vessel grouping index (VG), Vessel lumen fraction (F), and Xylem theoretical conductivity (Ks); physiological traits: Leaf predawn (ψPD) and midday (ψMD) water potential, and pressure-volume curve traits. All species adjusted their traits in response to water availability. Manilkara elata, the species with the highest wood density, exhibited smaller anatomical and hydraulic trait variations, with only a decrease in turgor loss point through osmotic adjustment under water limitation. The two species with lower wood density showed contrasting responses. Bertholletia excelsa enhanced hydraulic efficiency by increasing specific hydraulic conductivity, vessel area, and hydraulic diameter, while C. fairchildiana increased drought resistance by adjusting turgor loss point and osmotic potential. Our results highlight a trade-off between water transport efficiency and drought resistance, indicating distinct responses that contribute to species survival under water limitation.